in Computer Networks retagged by
5 votes
5 votes
Suppose you needed to use HTTP to download a webpage with three embedded images. The total number messages saved between the client and server starting from initiates TCP connection to receive the third object and close connection when using persistent HTTP without pipelining insteed of non-persistent HTTP are
in Computer Networks retagged by

1 comment

I doubt if the messages are saved at client/server side when the connection is actaully established. They are like request/response type messages.

That would depend upon the window size at the network layer, right?

1 Answer

18 votes
18 votes
Best answer

Persistent HTTP with pipelining and without pipelining:

  1. HTTP without pipelining: The client issues a new request only when the previous response has been received.: Total RTTs : 2 RTT + n RTT (n number of documents)
  2. HTTP with pipelining:      Total RTTs : 2RTT + 1RTT

Note: HTTP/1.1 uses persistent with pipelining.

selected by


edited by
In Non Persistence HTTP connection new connection will be stablished for every object

Therefore, for 3 objects – 2RTT + 3*2RTT = 8RTT

So, 8 RTT means 16 messages.

But what if the question had 10 objects with 6 parallel connections ???

Hi, I think made easy answer is correct because.

  • In non-persistent mode:

For each object there will be connection establishment, object transfer and connection termination.

Total RTT for one object = 1 RTT (connection establishment) + 1 RTT (object transfer) + 1 RTT (connection termination) = 3 RTT.

As we have total 3 objects hence we will multiply the RTT for 1 object by 3 as for each object connection establishment, object transfer and connection termination is required.

Total RTT (Non- persistent ) = 3 * 3 RTT= 9 RTT. 

Hence total message= 9 * 2= 18 message.


  • In persistent mode:

Only 1 connection establishment, 3 object transfer and 1 connection termination.

Total RTT (Non- persistent ) = 1 RTT (Connection establishment) + 3 RTT (Object Transfer) + 1 (connection transfer) = 5 RTT . 

Hence total message= 5 * 2= 10 message.


So message saved in Persistent mode over non-persistent mode = 18-10= 8 messages.

Note: None of the answer here already given considers the connection termination RTTs IDK why.

Best explaination

Related questions